a) Field of the Invention
The present invention is directed to a device for transferring a transport object between two end positions in which a stationary part supports a part which is movable linearly between the end positions by means of a drive, wherein the stationary part contains a supply unit for supplying signal current and motor current to sensors and actuators.
b) Description of the Related Art
In the production of integrated circuits, semiconductor wafers must be transported between different processing steps to individual processing machines. This is effected to an increasing extent in standardized transport containers, so-called Standard Mechanical InterFace boxes (SMIF boxes), since, instead of optimizing conventional clean rooms by way of higher grades of purity to achieve greater density of integration, rigorous implemented use of enclosures or the use of SMIF technology in semiconductor processing installations provides a way to achieve higher yields at reasonable cost.
The semiconductor wafers are inserted into shelves of a magazine which is attached in a suitable manner to the bottom of the SMIF box. In order to charge the semiconductor processing installations, the magazines are first removed from the transport containers. This generally necessitates a transfer which is carried out by various known technical solutions.
For example, in EP 209 660 a cassette is transported from a SMIF elevator to a device elevator by an automated cassette manipulator in that a swiveling movement is effected during the vertical movement for lifting or lowering the cassette. The use of rotating members is intended to reduce the degree of particle generation compared with linearly moving members.
Similar solutions are also described in EP 238 541, in which the magazine is transferred along given movement curves by motor-operated lever arms which are moved in the Z-direction by means of a separate lift.
The laminar flow of air required to maintain the clean room is perturbed or prevented due to the mechanical construction in the known solutions, in particular due to the fact that the region of action of the transfer device, which is constructed as a lever arm, is controlled laterally to the magazine and due to the closed design. Coupling the transfer movement with the Z-movement unnecessarily prolongs transport times and increases particle generation.
Moreover, when refitting semiconductor processing installations, it is difficult in the known technical solutions to supplement already existing clean rooms with the SMIF system so as to allow wafer magazines to be introduced into the machines under SMIF conditions and unpacked and transported in the machines under clean room conditions.
In a technical solution known from DE Patent 43 26 309 C1, a linear drive for a rigid gripper arm is attached to a supporting column for the purpose of transferring the magazine from a depositing position to a processing location, this linear drive being vertically adjustable in the movement direction of the elevator. The range of action of the gripper arm lies above the magazine located in the depositing position and is directed vertically to the movement direction of the elevator. An air passage opening is provided between the supporting column and an elevator drive. All drive parts are separated from the clean room by a dust-tight enclosure and suction devices or extractors are arranged adjacent to openings through which transport elements project into the clean room.
Although the disadvantages mentioned above are eliminated in this way, cables which are carried along over long transporting distances for transmitting signal current and motor current from devices provided for this purpose in the stationary part of the arrangement to movable parts can lead to disturbances and can have a negative impact on dependability. Mechanical reaction of the cable connection on the movable parts and the possibility of particle generation represent a further disadvantage.
Moreover, due to their wide variety, semiconductor processing installations also require different charging and depositing variants for the magazines.
Further, pneumatically operated linear drives have the disadvantage that they are braked very abruptly in end positions on either side of the cylinder by a speed control via throttle check valves in the form of an end position damping. In so doing, braking is effected from the maximum speed to zero along a distance of a few millimeters resulting in inevitable jolting of the transport object.